Lacquer, enamel, base solution, and the like



Patented July 16, 1935 UNITED *sTATEs PATENT- ,."I O FFlCIE No Drawing.

This invention relates to an improvement in lacquer, and more especially to cellulose ester lacquers as, for example, nitrocellulose lacquers and so-called nitrocellulose base solutions. It has heretofore been recognized that lacquers, including a cellulose ester, as for example, nitrocellulose or other cellulose ester, solvents,diluents, gums, plasticizers, etc., etc. and 'so-called base solutions or solutions of a cellulose ester, as nitrocellulose in a solvent or solvent'mixture and with the use of which lacquers may be formulated, became discolored on storage inmetallic containers such as tin plated cans, iron drums, and the like. Discoloration of lacquers is more noticeable in and consequently a primary disadvantage of so-called clear or unpigmented lacquers and in lacquers containing a white or light colored pigment. Discoloration is likewise disadvantageous in the case of so-called base solu-' I,

" Burney & Nollau patent, but that the limitations tions, which are unpig mented.

Discoloration of lacquers and base solutions isbelieved to be caused by corrosive action of the lacquer or some of its ingredients on metallic containers, with the formation and dissemination through the lacquer of a reaction product or products of poor color. In other words, it is believed that discoloration of lacquers in base solutions results from inadvertent contamination v a of the lacquer by a product or products of corrosion of metal containers.

Now, it is the object of this invention'to provide means for avoiding the discoloration of lac quers, enamels, base solutions, or the like, on storage in metal containers, such as'tin plated cans, iron drums, and the like. In other words, to provide a lacquer, enamel, base solution, or the like, of such a character that discoloration thereof upon storage in metallic containers, such as tin plated cans, iron drums, and the like, will be avoided.

In accordance with this invention, it has been found that phosphoric acid and salts thereof have a capacity for preventing the discoloration of lacquers, enamels, base solutions and the like.

not deleteriously effect the lacquer.

As has been indicated, salts of phosphoric acid may be used equivalently for phosphoric acid in amounts by weight on the nitrocellulose to give a phosphate'ion concentration equivalent to phos- "Application November 16,1933,- l 1 Serial No.698,362 I I v f 6 Claims. (or 134 79) pho'ric acid within about, the ratios specified above for phosphoric acid, and variously substantially inexcess thereof. d I It is appreciated that heretofore the addition. of phosphoric acid to ajlacquer has been jsugj gested by the patent to McBurney &' Nollau No. 1,836,264, dated December 15, 1 931, for'thepur pose of preventing livering or gelatinization of lacquers pigmented with a bronze powder. It will be understood, however, that this invention is clearly'differentiated from the disclosure of the McBurney '81 Nollau patent by virtue of the fact that theuse of phosphoric acid within the limits in accordance with this invention will notsub stantially. prevent .liveringor gelatinizingnof lac.- quer .pigmented'with a bronze powder.- Thus,;it: will be noted that the function of theuse of phos-i phoric acid according to this invention is not only entirely distinct from the disclosure of the -Mcupon the amountof phosphoric acid used in accordance with this invention are such that the function of the use ofphosphoric acid according.

to McBurneytz Nollau is not'obtained.

As' has been'indicate'd, in accordance withthis invention salts of phosphoric acid, as for eXam-' ple, tripotassium phosphate, dihy dr'ogen 1nono-' potassium'phosphate, monohydrogen dipotassiurn phosphateyetc etc) and corresponding sodium salts may be used equivalently for phosphoric acid; Generally speaking, where a "salt" of phosphoric acid is used, it will beused inamount, by weight on the'nitrocellulose contained in the lacquer or base solution, such as toprovidein thelacquer or base solution aipho'sphate' ion con-- centration equivalent tothat obtainable with the use of phosphoric acid within the limits indicated." However, where a salt otphosphoric acidis used, it may, if desired, be used in amount very-greatly in excess of the maximum amount of phosphoricacid, it being noted thatthe optimum amount of a salt of phosphoric acid will depend upon the particular lacquer, formulation. Thus, for ex ample, as' much as 4% by weighton'the nitrocellulose of a salt of phosphoric'acid may be used,'it'

being noted, however, in such amount salts of phosphoric acid will not prevent livering or gelatime, it will be noted that if the lacquer be pigmented with a bronze powder, livering will not be substantially prevented.

Where a salt of phosphoric acid is used, in most formulae the salt may be used in amount to give a phosphate ion concentration equivalent to that provided with the use of about 0.07% to 0.08% phosphoric acid by weight on the nitrocellulose. The amount of salt necessary to give an equivalent phosphate ion concentration with respect to phosphoric acid is found by multiplying the desired phosphate ion concentration by the ratio of the molecular weight of the salt chosen and the molecular weight of phosphate ion (P04) Thus, where a phosphate ion concentration of 0.0097% is desired, and which would be provided by the use of 0.01% of phosphoric acid, the necessary calculation may be exemplified in the case of trisodium phosphate NasPO412H2O as follows:

From the above example, it will be noted that for the provision of a phosphate ion concentration of 0.0097% a' salt of phosphoricacid, e. g. trisodium phosphate, in amount of 039% by Weight on the nitrocellulose would be used.

As more specifically illustrated, for example, a base solution which will be substantially resistant to discoloration on storage in a metal container may be made up on the following formula:

Per cent Nitrocellulose, viscosity second 20 Ethyl alcohol -f 20 Ethyl acetate l6 Toluol 44 Discoloration of a base solution on the above formula will be prevented by the addition of, for example, about 0.07 of phosphoric acid by weight on the nitrocellulose, and likewise by the addition of a salt of phosphoric acid in amount to give an equivalent phosphate ion concentration. The base solution may be stored withoutany substantial discoloration and may be used for the formulation of lacquers and enamels by admixture with resins, plasticizers, pigments, etc., such as are ordinarily and widely known to the art for use in the formulation of lacquers.

The phosphoric acid or salt of phosphoric acid will desirably be thoroughly incorporated with the base solution and may be added as such, though addition will be preferably made through the medium of a solution in alcohol or one of the solvents to be included in the base solution or lacquer.

Further, while it is appreciated that the addition of phosphoric acid to lacquers, enamels, etc. pigmented with bronze powder has heretofore been suggested for the prevention of livering, it is noted that when added to a lacquer, enamel or base solution pigmented with bronze powder in an amount such as will effectively prevent discoloration and, at the same time willnot deleteriously effect nitrocellulose, it does not substantially prevent livering.

Where salts of phosphoric acid are used, they like phosphoric acid have been found to have a capacity for preventing discoloration. However, though they may be used within substantially wider limits than need be phosphoric acid, they like phosphoric acid, within the limits indicated, will not prevent livering of lacquers or enamels pigmented with bronze powder.

It will be understood that the phosphoric acid or a salt thereof may be incorporated in a base solution, or a lacquer as such or with nitrocellulose per se'intended for use in the production of base solutions or lacquers.

It will be understood that in accordance with this invention salts of phosphoric acid are equivalents for phosphoric acid, it being noted, however, that salts of phosphoric acid may be used within very substantially wider limits than phosphoric acid.

This application is. a continuation in part of my application Serial No. 602,391, filed March 31,

WhatI claim and desire to protect by Letters Patent is: 7

1. In combination, a cellulose ester, a solvent therefor and phosphoric acid in amountwithin about the range 0.01-0.2% by weight on the cellulose ester.

2. In combination, nitrocellulose, a solvent therefor and phosphoric acid in amount within about the range 0.01-0.2% by weight on the nitrocellulose.

3. In combination, a cellulose ester, a solvent therefor and a substance from the group consisting of phosphoric acid and ionizable salts of phosphoric acid the substance being present in amount to give a phosphate ion concentration equivalent to that given by phosphoric acid in amount within about the range 0.01-0.2% by weight of the cellulose ester.

4. In combination, nitrocellulose, a solvent therefor and a substance from the group consisting of phosphoric acid and ionizable salts of phosphoric acid the substance being present in amount to give a phosphate ion concentration equivalent to that given by phosphoric acid in amount within about the range OBI-0.2% by.

weight of the nitrocellulose.

5. A cellulose ester solution including a cellulose ester and a solvent therefor, said solution a phosphate ion concentration equivalent to that given by phosphoric acid in amount within about the range 0.07-0.08% of phosphoric acid by weight onthe nitrocellulose ester contained in the solution.

CARL B. GILBERT. 

